Test structure and test method for online detection of metal via open circuit

A test structure for online detection of a metal via open circuit, comprising:

• a doped substrate;
• a contact layer on the doped substrate;
• a first metal layer on the contact layer;
• a first metal via layer on the first metal layer;
• a second metal layer on the first metal via layer;
• a second metal via layer on the second metal layer;
• a third metal layer on the second metal via layer;
• a third metal via layer on the third metal layer;
• and
• a fourth metal layer on the third metal via layer,
• wherein the contact layer comprises a plurality of contacts, the plurality of contacts being connected to the first metal layer, the first metal via layer comprises a plurality of first vias, the plurality of first vias being filled with metal, and the plurality of first vias being connected to the second metal layer.